Before, the inventor of the present invention developed a television receiver having Internet functions, and has proposed a transmission/reception system with a configuration including a base-station apparatus and a monitor apparatus connected to the base-station apparatus by radio communication.
Typically, since a reception antenna for television broadcasting can be connected to the base-station apparatus of the transmission/reception system, the base-station apparatus is capable of selecting a television broadcast signal, receiving a selected television broadcast signal and demodulating a received television broadcast signal. In addition, the base-station apparatus is capable of converting a video signal obtained in this way into compressed video data as well as outputting and transmitting the compressed video data. Furthermore, by employing a modem, the base-station apparatus can be connected to the Internet by using a telephone line. Moreover, the base-station apparatus also has a browser function for displaying data, which is received from a web site typically by way of the Internet, as an image. In addition, the base-station apparatus also has an email function. The base-station apparatus is capable of outputting/transmitting displayed data of a mail application and information of a browser image obtained by using the browser function as compressed video data.
The monitor apparatus has such a small size that the user is capable of carrying about the apparatus in a room for example. The monitor apparatus decodes video data transmitted by the base-station apparatus and displays an image as well as outputs a sound as results of decoding. In addition, the monitor apparatus also allows the user to carry out operations against the browser screen and operations manipulating emails. Information generated as a result of such an operation is transmitted to the base-station apparatus. In the base-station apparatus, browser and email applications operate in accordance with operation information received from the monitor apparatus so that accesses to the Internet can be made and emails can be sent and received.
With such a transmission/reception system, the user is allowed typically to carry about the monitor apparatus or put the apparatus at any arbitrary place. That is to say, the user is capable of watching a television broadcast and making use of the Internet at any arbitrary place as long as the place is in a domain allowing communications.
FIG. 8 is a block diagram showing members for mainly transmitting and receiving data in internal configurations of a base-station apparatus and a monitor apparatus, which compose the transmission/reception system described above.
In the base-station apparatus 50, AV (Audio and Visual) data is supplied to an AV encoder 51. The AV data is obtained as a result of converting an image/sound signal such as a television signal into digital data. The AV encoder 51 compresses the AV data by adoption of a predetermined image/sound compression technique.
Compressed AV data output by the AV encoder 51 is supplied to a first communication-protocol-processing unit 52 for carrying out processing including a process to enclose the data in a packet conforming to a predetermined communication protocol.
In the case, a first control unit 54 controls the AV encoder 51. For example, the first control unit 54 controls the AV encoder 51 to change the compressibility (data rate) in accordance with a reception state reported by the apparatus on the reception side.
The first communication-protocol-processing unit 52 is a special-purpose circuit for carrying out communication protocol process. The first communication-protocol-processing unit 52 constitutes hardware for carrying out transmission/reception processes according to a communication protocol.
The first communication-protocol-processing unit 52 carries out a necessary transmission process according to the communication protocol on input AV data to be transmitted. An example of the transmission process is a process to enclose the AV data in a packet. Data completing the transmission process is then supplied to a first transmission/reception unit 53.
The first transmission/reception unit 53 outputs the input data as an electromagnetic wave by adoption of radio communication.
Furthermore, the base-station apparatus 50 may transmit data other than AV data. Examples of the other data are data related to email and communication control information. In this case, in the configuration shown in the figure, the other data is supplied to the first communication-protocol-processing unit 52 under control executed by a first control unit 54. Thus, the other data is also transmitted from the first transmission/reception unit 53 by using radio communication.
In addition, the first transmission/reception unit 53 also receives data transmitted by the monitor apparatus 60 and then passes on the data to the first communication-protocol-processing unit 52. In this case, the first communication-protocol-processing unit 52 extracts the data from a packet in accordance with the communication protocol and then supplies the data typically to the first control unit 54. Then, the first control unit 54 carries out necessary control processing on the data on the basis of the substance of the data supplied thereto.
Data transmitted by the base-station apparatus 50 to the monitor apparatus 60 is received by a second transmission/reception unit 61 employed in the monitor apparatus 60 before being supplied to a second communication-protocol-processing unit 62.
For example, the second communication-protocol-processing unit 62 receives compressed AV data as input data received from the second transmission/reception unit 61. In this case, the AV data is supplied to an AV decoder 63. The AV decoder 63 decodes the compressed AV data and outputs typically AV data as a result of decoding. A display unit not shown in the figure shows an image based on the AV data received from the AV decoder 63 typically on a display screen of the monitor apparatus.
The data supplied to the second communication-protocol-processing unit 62 may be other than compressed AV data. Also in this case, the second communication-protocol-processing unit 62 supplies the data other than compressed AV data to a second control unit 64.
In addition, the monitor apparatus 60 may transmit necessary information to the base-station apparatus 50 as transmission data. For example, the second control unit 64 monitors an operation carried out by the AV decoder 63 and sets a proper compressibility for compressed AV data in accordance with an error. Then, as necessary information, the monitor apparatus 60 transmits control information to the base-station apparatus 50. On the basis of the control information, the AV encoder 51 employed in the base-station apparatus 50 is capable of carrying out a compression process at the set compressibility.
In such a case, the second control unit 64 supplies the data to be transmitted to the second communication-protocol-processing unit 62. The second communication-protocol-processing unit 62 then carries out processing according to a predetermined communication protocol on the data to be transmitted. The processing includes a process to enclose the data to be transmitted in a packet. The packet is then transmitted from the second transmission/reception unit 61 by a radio communication.
FIG. 9 is a block diagram showing internal configurations of another base-station apparatus and another monitor apparatus. It is to be noted that the figure also shows only members for mainly transmitting and receiving data. In addition, members identical with their counterparts shown in FIG. 8 are denoted by the same reference numerals as the counterparts and their explanation is not repeated.
The first communication-protocol-processing unit 52 and the first control unit 54, which are employed in the base-station apparatus 50 shown in FIG. 8, are omitted. Instead, a first CPU 55 is employed in the base-station apparatus 50 shown in FIG. 9.
The first CPU 55 carries out transmission data processing according to a communication protocol on data to be transmitted such as compressed AV data received from the AV encoder 51. The transmission data processing includes a process to enclose the compressed AV data in a packet. The first CPU 55 then drives the first transmission/reception unit 53 to transmit data obtained as a result of the processing to the monitor apparatus 60. The base-station apparatus 50 may transmit data other than AV data to the monitor apparatus 60. Also in this case, the first CPU 55 carries out transmission data processing according to the communication protocol on the other data. The transmission data processing includes a process to enclose the other data in a packet. The first CPU 55 then drives the first transmission/reception unit 53 to transmit data obtained as a result of the processing to the monitor apparatus 60. The first transmission/reception unit 53 carries out reception data processing according to the communication protocol on data received from the monitor apparatus 60. The reception data processing includes a process to extract the received data from a packet enclosing the data.
In addition, the first CPU 55 also controls the AV encoder 51 to change the compressibility (data rate) in accordance with the reception state reported by the apparatus on the reception side.
As described above, the base-station apparatus 50 shown in FIG. 9 carries out processing according to a communication protocol by execution of a program on data to be transmitted and received-data in addition to processing to control components such as the AV encoder 51. As described above, the processing according to a communication protocol includes a process to enclose data to be transmitted in a packet. That is to say, the first CPU 55 employed in the base-station apparatus 50 has the functions of the first communication-protocol-processing unit 52 and the first control unit 54, which have been described earlier. In particular, the processing according to a communication protocol is carried out by execution of software.
By the same token, the monitor apparatus 60 shown in FIG. 9 employs a second CPU 65 as a substitute for the second communication-protocol-processing unit 62 and the second control unit 64, which are shown in FIG. 8.
Thus, the second CPU 65 employed in the monitor apparatus 60 has the functions of the second communication-protocol-processing unit 62 and the second control unit 64, which have been described earlier. In particular, the processing according to a communication protocol is carried out by execution of software.
In the configurations of the base-station apparatus 50 and the monitor apparatus 60, which are shown in FIG. 8, the processing according to a communication protocol is carried out by the first communication-protocol-processing unit 52 and the second communication-protocol-processing unit 62, which are each a special-purpose circuit implemented by hardware. Thus, the transmission/reception system offers a merit that the processing can be carried out at a sufficiently high speed even for data having a high data rate and imposing a requirement for time-series continuity as is the case with AV data. On the other side of the coin, however, if the processing according to a communication protocol is entirely carried out by using hardware, the expandability is poor. For example, if the communication protocol is somewhat changed, there is raised a problem of a difficulty to keep up with such a change.
In the base-station apparatus 50 and the monitor apparatus 60, which are shown in FIG. 9, on the other hand, the processing according to a communication protocol is carried out by using software. Thus, in order to keep up with changes such as a change in communication protocol, the program executed to carry out the processing according to a communication protocol is just modified. It is therefore easy to keep up with such a change and there is no cost. Such configurations of the base-station apparatus 50 and the monitor apparatus 60 are advantageous from the extensibility point of view. However, they are disadvantageous from the processing-speed point of view. In the present state of the art, in particular, in order to carry out the processing correctly for data having a high data rate and imposing a requirement for time-series continuity as is the case with AV data handled in the transmission/reception system described above, it is necessary to use a component such as a CPU with an extremely high speed. As a result, a very high cost will be incurred.